1. Field of the Invention
The present invention relates to a conveyance apparatus for conveying a printing medium and, more particularly, to processing of a printing medium that remains retained within a conveyance apparatus in the process of being conveyed through the apparatus.
2. Description of the Related Art
In a conveyance apparatus for conveying paper, paper jam, which is a phenomenon in which the paper is not conveyed properly and remains retained in the conveyance path, often occurs. If conveyance is allowed to continue with the paper left jammed inside the apparatus, the next sheet of paper also will experience jamming. The jammed sheet of paper, therefore, must be removed. In addition, it is necessary that the occurrence of a paper jam be sensed accurately.
The specification of Japanese Patent Laid-Open No. 8-245062 proposes a method of sensing the position of jammed paper by placing in the conveying path a number of sensing units to sense whether or not paper is present. The specification of Japanese Patent Laid-Open No. 2005-221522 proposes a method whereby paper situated in a double-sided conveyance unit is discharged to the exterior of the apparatus in a direction opposite the normal conveyance direction and at a speed higher than the normal conveyance speed.
However, in a conveyance apparatus in which the paper is partially exposed to the exterior of the apparatus and the direction of paper conveyance is reversed, a state in which the paper cannot be sensed by any sensing unit arises. In this case, it may not be possible to specify where the paper is situated even if jamming of the paper in the paper conveyance apparatus has been sensed, and therefore it may not be possible to indicate the proper paper removal method to the user.
As a consequence, there are occasions where the user opens and closes a door that is unrelated to paper jam. Generally, when a door of an image forming apparatus is opened, power to a fixing device and other devices turns off and the fixing device cools. Since it takes time for the temperature of the fixing device to recover, downtime during which printing cannot be executed results. Further, if jammed paper is not removed properly, jamming is worsened by succeeding sheets of paper and the apparatus may malfunction.